International application WO2005/007185 describes attempts to stabilize protein pharmaceuticals without the addition of the often used stabilizer human serum albumin (HAS). The stabilizing solution employed in WO2005/007185 instead comprises (i) a surface-active substance that is preferably a non-ionic detergent, i.e. a surfactant and (ii) a mixture of at least two amino acids, wherein the at least two amino acids are either glutamate and glutamine or aspartate and asparagine. The sole example testing the stabilizing effect of amino acids on their own (table 2) shows that in the absence of the surfactant polysorbat 80, no or only insubstantial stabilization—for a limited amount of time—of the protein solution was found.
In the international application WO 2008/000780, a spray dried powder containing protein is stabilized and has an advantageous aerodynamic behavior when at least 30% or at least 40% phenylalanine are included. Due to the addition of phenylalanine in the powder, the cohesive and adhesive properties of the powder are altered to reduce the interactions between the particles. By rendering the surface of the powder particles more hydrophobic, the aerodynamic properties of the powder are improved, thus rendering it more suitable for pulmonary application. The induction of folding or prevention of unfolding of proteins by a solution containing amino acids is not envisaged in WO 2008/000780.
European Patent application EP 1789019 describes spray dried powders of protein drugs for pulmonary application that are stabilized by the addition of novel oligosaccharide mixtures. International application WO 2010/151703 discloses a pharmaceutical composition for increasing the stability, reducing aggregation or reducing immunogenicity of a peptide or polypeptide, comprising at least one alkylglycoside.
In summary, it is crucial that the formulation scientist has a thorough knowledge of several factors: how to optimize the physical and chemical stability of the active ingredient; how, rationally, to include specific excipients in the formulation; how to obtain the optimum conditions for stability; how to prevent stability issues during up-scaling; and, finally, how to design a formulation that is suitable for the intended route of administration, that is, one that allows the absorption barrier to be overcome. The choice of excipients is often based on previous experience and on which excipients have been approved by authorities. Excipients are generally chosen (i) to ensure a successful end point for a preparation process, for example, allowing a dry powder to be obtained; (ii) to ensure that a liquid formulation remains at constant pH value; or (iii) to stabilize the protein against a certain production induced effect, for example adsorption. However, what may be useful for one protein can have detrimental effects on another.
The large size of proteins, their compositional variety and amphiphatic characteristics constitute specific behavior such as folding, conformational stability, and unfolding/denaturation. The structural differences among different proteins are so significant that generalization of universal stabilization strategies has not been successful to date. Despite the fact that a lot of research is invested into providing suitable methods to prevent unfolding and/or ensure proper folding of proteins during the exposure to the different forms of stresses, there are still problems with e.g. aggregation or increased unspecific immunogenicity due to protein misfolding. Even more, to date, the basic properties of a protein usually need to be examined prior to the development of a stable protein formulation. These properties include protein purity, pI as well as solubility and stability at different pH and in different buffer systems. With these data, protein formulation issues are usually addressed.
While it is desirable to keep the number of functional excipients as low as possible, for example in order to reduce instability resulting from solid state interactions, the vast amount of potential destabilizing effects often necessitates the addition of several excipients. Furthermore, for each protein of interest, cumbersome investigations are necessary to identify the respectively suitable excipients. Consequently, there is still a need to provide improved means to fold proteins or to prevent their unfolding during the exposure to the different forms of stresses upon the production and storage process that overcome these problems and are suitable for the majority of proteins and peptides, eliminating the need for individual investigations.
This need is addressed by the provision of the embodiments characterised in the claims.